In any case, I did this design over a year ago; Pulsestrike tanks make for wonderful Nerf conversions. The usefulness for homemade water guns still remains, though. So I figure you can take what you want of the design, and adapt it for your own purposes. I'm working on a newer version myself; I can update the thread once that's done.
Original post: HERE
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As many of you know, the Pulsestrike is one of the most awesome water guns for conversion to Nerf. With a pump replacement, it easily rivals the Titan in terms of power, but for much less money. A homemade version also requires perfect chamber sealing...something that's hard to achieve.
After several experiments with repair couplings and other things, I fell back to my first homemade writeup for inspiration. Instead of looking for a preassembled chamber, I would modify my earlier design of the piston inside the B.U.F.F. for better sealing. That, combined with an amazingly easy to open ball valve, made for a blaster with lots of power.
Parts list:
Blaster body:
1 1/4" PVC
1" to 1/2" PVC bushing
1 1/4" PVC tee
1/2" PVC
1/2" PVC tee (with the tee off threaded)
1/2" Sch. 80 PVC ball valve made by KBI
Internals:
(2) 3/4" PVC caps, with large hexagonal ends (made by Genova?)
3/4" PVC coupling
(2) AS568A-216 o-rings (1 1/8" ID, 1 3/8" OD)
Your choice of skirt seal/superlative plunger head/etc. Look them up.
(3) 3/4" PVC caps
(2) Hillman #49 springs
Pump/grip:
Whatever pump you choose, and the fittings required to convert to 1/2" Male threaded PVC
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Here's the new version of the internal piston. Under ideal construction, you would use a 3/4" coupling, and 2 3/4" plugs. Specifically, the kind with large hexagonal ends that you can shave down to fit ever so loosely into 1 1/4" PVC. In a nod to overengineering, I went ahead and added a skirt seal to the side that faces the barrel. Normally, I'd use polycarb circles and McMaster skirts, but none were handy. I improvised and took the skirt seal from a broken Marshmallow blaster, which fits perfectly in the 1 1/4" pipe.
Now we can place springs behind it. I used 3/4" PVC caps to keep the springs lined up to minimize issues. Pictured are Hillman #49 springs. Since then, I've nested other random springs inside the #49s. a 1 1/4" PVC tee will cap the back of the blaster, acting as the spring rest and the shoulder stock.
The main work is done. I capped the frot of the chamber with a 1" to 1/2" bushing (with a wrap of tape and JB weld). The bottom of the tee is threaded, allowing use of the Dual Action pumps from my Modular Air Gun System. on the front is a KBI 1/2" Sch. 80 PVC ball valve. Aside from the initial opening force, it is amazingly easy to open all the way - the result being performance like the spring-loaded ball valves in some Super Soakers. I'll throw a longer handle on there, so that I can use the bike pump as the grip and have a normal trigger.
UPDATE: My design allows for disassembly from the backside. Which means different spring combos. You can use a spacer to replace your extra springs!
There are several issues to deal with:
-SHEER POWER. I was aiming for this kind of power; however, aside from a massive shotgun or rocket launcher, it has little nerf war use. Make it smaller, with one smaller but stiff spring (or precompressed spring, if for some reason, you only have a K26 laying around...)
-OPV. There currently is none. I'm looking at the possibility of placing a tiny hole in the 1 1/4" PVC pipe. Presumably, once you've filled the chamber enough to pass that hole, it will bleed out, and the spring will seal it off again.
-Plunger padding: I need to do this ASAP, as there is a ton of force being applied. You will have to do it as well.
Firing video:
http://www.youtube.com/watch?v=Zwp_zPc33VQ
Questions/comments/flames can now proceed.
